﻿/*
  KeePass Password Safe - The Open-Source Password Manager
  Copyright (C) 2003-2014 Dominik Reichl <dominik.reichl@t-online.de>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;

using KeePass.Native;

using NativeLib = KeePassLib.Native.NativeLib;

namespace KeePass.Util
{
    public sealed class ClipboardEventChainBlocker : IDisposable
    {
        private ClipboardBlockerForm m_form = null;
        private IntPtr m_hChain = IntPtr.Zero;

        public ClipboardEventChainBlocker()
        {
            if (NativeLib.IsUnix()) return; // Unsupported

            m_form = new ClipboardBlockerForm();

            try
            {
                m_hChain = NativeMethods.SetClipboardViewer(m_form.Handle);
            }
            catch (Exception) { Debug.Assert(false); }
        }

        ~ClipboardEventChainBlocker()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool bDisposing)
        {
            if (m_form != null)
            {
                try
                {
                    if (NativeMethods.ChangeClipboardChain(m_form.Handle,
                        m_hChain) == false)
                    {
                        Debug.Assert(false);
                    }
                }
                catch (Exception) { Debug.Assert(false); }

                m_form.Dispose();
                m_form = null;
            }

            m_hChain = IntPtr.Zero;
        }

    private sealed class ClipboardBlockerForm : Form
        {
            public ClipboardBlockerForm()
                : base()
            {
                this.Visible = false;
                this.ShowInTaskbar = false;
                this.ShowIcon = false;
            }

            public override bool PreProcessMessage(ref Message msg)
            {
                if (msg.Msg == NativeMethods.WM_DRAWCLIPBOARD)
                    return true; // Block message

                return base.PreProcessMessage(ref msg);
            }
        }
    }
}
